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The bacon chow study: effects of maternal nutritional supplementation on infant mental and motor development

Sandra K. Joos, Ernesto Pollitt, and William H. Mueller
The University of Texas Health Science Center, School of Public Health, Houston,
Texas, USA

INTRODUCTION

Over the past 15 years, four large-scale experimental nutritional
supplementation studies have been conducted in Guatemala, Bogota, New York City,
and Taiwan (1-3). Each of these studies included some control over dietary
intake, longitudinal evaluations, and measurements of the effects of maternal
supplementation on the behavioural development of infants and children. However,
the results of the Taiwan study have not been available because of the death in
1973 of the principal investigator, Dr. Bacon Chow of the Johns Hopkins School
of Hygiene and Public Health.

In 1967 Dr. Chow initiated a study in Taiwan to determine whether a protein
and calorie supplement to mothers during pregnancy and lactation would have a
beneficial effect on the growth and development of their infants. Because
experiments with rats indicated that protein deficits in the maternal diet
during pregnancy and lactation had the greatest negative effects on physical and
behavioural development, the primary aim was to study supplementation of the
diets of mothers who had a marginal protein intake rather than of obviously
undernourished mothers (4). A rural population in Taiwan with low protein intake
but no frank malnutrition was chosen, and the study was conducted over a 6
1/2-year period, from 1967 to 1973.

Associates of Dr. Chow have published preliminary findings (5, 61. Further
analyses of dietary and supplement intake, birth weight, growth, and behavioural
development have been completed since Dr. Ernesto Pollitt received a copy of the
data tapes in 1978 (7-11). A summary of the results of an analysis of the
effects of maternal supplementation on the mental and motor development of the
Taiwan infants at eight months of age is presented here.

METHODS

Design

The Bacon Chow study was a randomized, controlled, double-blind trial of
nutritional supplementation of pregnant and lactating women. Two hundred
ninety-four pregnant women were randomly assigned to one of two groups. Group A
received a high-calorie and protein supplement (800 kcal, 40 9 protein per day),
while group B received a placebo. (Until June 1970 formula B, the placebo,
contained only 6 kcal per day; thereafter, it contained 80 kcal, no protein per
day.) Both the supplement and the placebo were liquid formulas packaged in 121/2
ounce (375 ml) cans and were similar in taste, texture, and weight. All women
also received a multivitamin and mineral tablet daily.

The supplement or placebo was given to each mother beginning three weeks
after the delivery of the first infant born to her after the study began. It was
continued throughout the lactation of this infant, through the interpregnancy
period, and through the pregnancy and lactation of the second infant she
delivered during the study. No supplement was provided directly to the infants.
Each mother, then, provided two "study" infants and was given
supplement or placebo during the gestation of the second, but not the first,
infant.

Subjects

The study was conducted in 14 villages in Sui-lin Township, an economically
distressed agricultural region about 180 miles south-west of Taipei, Taiwan. The
diet of the population was limited mainly to rice, sweet potatoes, and other
vegetables, with little animal protein. The 294 women selected for the study
were of lowest economic status and were considered to be marginally nourished. A
preliminary dietary survey of the women indicated that caloric intake was as low
as 1,200 kcal per day, and the daily protein intake (primarily of vegetable
origin) was less than 40 9. Lactation in this population continued until infants
were about 15 months of age, and all mothers began supplementing the infant diet
at around seven months (6).

The criteria for the selection of the study women included the following:
married, with one normal male child; in the third trimester of pregnancy;
planning to have at least one more child; 19 to 30 years old; and in
satisfactory health on physical examination, with normal values for haemoglobin,
plasma protein, and haematocrit (5). Of the 294 women recruited, 225 gave birth
to two infants within the study period. The 69 women who did not were almost
evenly divided between groups A and B.

Procedures

Both supplement and placebo were distributed twice daily by nurses, who
measured and recorded the volume remaining in the can after the women had drunk
the formulas. The percentage of the total volume consumed was averaged and
recorded monthly. Neither the mothers nor the nurses knew whether a can
contained supplement or placebo. The mothers' daily food intake was surveyed at
approximately three-month intervals. Duplicate samples of three meals were
collected in the homes by the nurses and analysed for nitrogen, fat, and
carbohydrate content. Between-meal eating was not assessed, and therefore the
total daily intake is probably underestimated. Nevertheless, the food survey
information does appear to reflect reliably the inter- and intra-group
variability in food intake over time (8).

Assessment of mental and motor infant development at eight months of age,
using a research version of the Bayley Scales of Infant Development, was begun
two years after the study was under way. Only 60 of the first study infants were
examined, while all but 14 of the second infants were. The testing was done by
two American-trained Chinese psychologists in a specially designed and equipped
room located at the central village in Sui-lin Township. We have no quantitative
data regarding inter-tester reliability, but one of the original investigators
has informed us that it was high (A.M. Hsueh, personal communication, 1980).

The infants were tested on 24 motor items and 50 mental items. Each item was
scored as passed or failed. Because of the large number of items that all
infants passed or failed, items were selected for this analysis if at least 10
per cent but not more than 90 per cent of the sample passed the item. Seven
items in the motor scale and 10 items in the mental scale met this criterion.
Scores of 0 to 7 on the motor scale and 0 to 10 on the mental scale are
therefore possible.

Because only a small number of first study infants were tested, this analysis
is restricted to a between-group comparison of the second study infants. Because
of the ordinal nature of the modified mental and motor scales, the statistical
analyses were based on non-parametric tests of group differences. However,
parametric tests were also calculated, and the results are presented.

Cases were excluded from this analysis for the following reasons: missing
information on the Bayley Scales (14 cases), on supplement intake by the mother
(2 cases), or on birth measurements- i.e., weight and anthropometry - (1 case);
the presence of congenital anomalies (5 cases); extremely low supplement intake
by mothers (4 cases); or an extreme age at testing ( 1 case). Twenty-seven cases
were thus excluded, leaving 198 cases evenly divided between groups A and B.

RESULTS

There were no significant differences (p < 0.05) between the groups in any
moderating variables that could influence the results of the between-group
Bayley Scales comparisons (i.e., maternal anthropometry and reproductive
characteristics, parents' education and scores on the Raven's Progressive
Matrices, and age of the infant at testing). Therefore, none of these variables
was controlled in the analysis. Although group-B mothers tended to consume
slightly more food at home than group A, because of the contents of the
supplement in group A, total intake in group A was substantially above that of
group B (about 400 kcal/day, on average) throughout pregnancy and lactation.

Table 1 presents the means and standard deviations of the mental and motor
scores of infants of mothers in the two groups, with males and females combined
and separated. The mental scores of group-A infants were no higher than those of
group-B infants, nor were there any sex differences in either group. The motor
scales of group-A infants were, however, higher than those of group-B infants,
and the difference is statistically significant.

Chi-square analysis of single items in the motor scales showed that the
majority of the difference in infants of group-A mothers is accounted for by
only three items: the ability of the infant to raise itself to a sitting
position, to pull itself up until standing, and to bring two objects together at
midline.

DISCUSSION

Maternal nutritional supplementation during pregnancy and lactation had no
effect on the Bayley mental-scale scores attained by infants at eight months of
age. There was a modest beneficial effect on the motor scores of infants of
mothers who consumed the high calorie and protein supplement, with the majority
of effect in only three items. No sex differences in response to the supplement
were detected. These findings are consistent with those of the Guatemala (1) and
Bogota (2) studies, in which effects of a nutritional supplement were also most
evident in motor items or subscales. The findings of these studies are also
similar in that the independent effect of nutrition on behavioural development
was not large in any of them.

In the Taiwan study, the small impact of the maternal supplement on infant
behavioural test performance despite the magnitude of the nutritional
intervention may have been caused by several factors. First, the population was
probably only marginally malnourished at the outset of the study. Second,
mothers who could have been at risk for poor birth outcome were excluded by the
selection criteria. Finally, the infants received no direct supplementation from
the investigators.

The finding of supplement effects on the motor-scale and not on the
mental-scale performance of Taiwan infants, and primarily on motor-scale items
in other studies, may have to do with the nature of developmental processes in
the first year of life. Infants interact with and experience their environment
primarily through the sensorimotor behaviours by which they manipulate and
explore their physical surroundings. Improvement in neuromotor and sensorimotor
functioning characterizes development at this age and would therefore be most
affected by prenatal environment and nutrition in the first year of life.

Overall, the benefit of maternal supplementation on the behavioural
performance of Taiwanese infants at eight months of age was small. Even though a
statistically significant difference exists between the motor scores of A and B
infants, and even if this can be attributed to the different levels of
nutritional supplementation of the mothers, the functional significance of this
difference is unresolved.

ACKNOWLEDGEMENTS

We gratefully acknowledge the contributions to this study made by Dr. R.
Quentin Blackwell and Dr. Janet Hardy.

Dr. Blackwell was the principal co-investigator during the data collection
period, and Dr. Hardy directed the assessment of infant development.

The data analysis was supported in part by the Ford Foundation and the Nestlé
Coordination Centre in Nutrition, Washington, D.C., USA

The organizers- the Department of Human Nutrition of the University of
Ibadan, in conjunction with the Nutrition Society of Nigeria, and the
International Union of Nutritional Sciences- extend an invitation to scientists
and others interested in nutrition research and its applications.

The languages of the congress will be English and French.

The registration fee is US$80 (N 501 if paid before 1 October 1982;
thereafter it will be US$160 (N 1001. Payment should be made to: Second African
Nutrition Congress, Department of Human Nutrition, University of Ibadan, Ibadan,
Nigeria.

Requests for information and all other correspondence should be sent to:
Prof. Adewale Omololu, Secretary-General, African Nutrition Congress, Department
of Human Nutrition, University of Ibadan, Ibadan,
Nigeria.